Physicochemical properties of new peanut (Arachis hypogaea L.) varieties

Peanuts (Arachis hypogaea L.) are one of the major oilseed crops of the world and are an important source of protein in many countries. In this study, some nutrients and characteristics of the seeds’ oil extracted from four peanut (Arachis hypogaea L.) varieties: Line 27r (Israel), Line 9 (Malawi), Line 4 (Brazil) and Line 18 (Israel) cultivated, for first time, in Upper Egypt were subjected to the comparative assessment with control NC variety (USA). Peanut seeds are a rich source of oil content (50.45 to 52.12 g 100 g−1 dry weight “DW”). The physicochemical properties of extracted oil were investigated in this study. The obtained data showed that the ratios of saturated fatty acids ranged from 14.24 to 17.23%, and the amounts of unsaturated fatty acids ranged from 82.77 to 85.76%. Significant variations (p ≤ 0.05) of oil content, saponification value, oleic/linoleic (O/L), and oil characteristics were found. Line 9 was found to be high in oil content, while Line 27r was said to have a high O/L ratio (3.22%) and proportion of unsaturated fatty acids (85.76%).


Introduction
Peanuts (Arachis hypogaea L.) are known as groundnuts and are related to the Leguminosae family. It is grown for oil extraction and also as a food product (Pasupuleti et al., 2013). More than a third of the peanut varieties grown on a global scale are used as food (Dhamsaniya et al., 2012). Peanuts are considered an important source of oil, folate, antioxidants, protein, and essential fatty acids (linoleic) (Sebei et al., 2013). Hence, consumers and industry fields have a growing interest in peanuts (Zhao et al., 2012). Peanuts are ranked fourth in oilseed crops in the world after soybeans, rapeseed, and cotton. In 2015, peanuts made up 8.7% of the total production of oilseed by contributing 45 million tons of world production. It is also an important oilseed crop for the production of vegetable oils (Arioglu, 2014). About 2/3 of the world's total peanut production is used to produce oil and the remaining 1/3 is used in food products (Variath and Janila, 2017). In Egypt, there is a great shortage in edible oils so that almost 90% of the consumption needs are currently imported (Zaher et al., 2017).
The ratio of saturated to unsaturated fatty acids in both crude oils and fats is more important to healthy nutrition (Zahran and Soliman, 2018). According to the American Heart Association (AHA) recommendations and National Health Service (NHS) UK guidelines, between 25 and 35% of your total daily calories should consist of fat. They indicate that the average adult can eat up to 70 g of fat a day, of which no more than 20 g should be saturated and 50 g unsaturated fats. The quality of peanut oil was determined by the ratio of oleic to linoleic acid and iodine value. In addition, the percent of unsaturated fatty acids and stability of peanut oil was determined using iodine value. High-oleic peanuts have a longer shelf-life than low-oleic peanuts and have the best flavor and stability than that of low-oleic peanuts (Chaiyadee et al., 2013;Gulluoglu et al., 2016). Peanut oil contains a high percentage of antioxidants in addition to a high proportion of polyunsaturated fatty acids, and this is desirable because it reduces the amount of cholesterol in the blood as well as lowdensity lipoprotein content, which may reduce the risk of coronary heart disease (Win et al., 2011).
This study was carried out to determine some nutrients physical and chemical properties, as well as fatty acid profile of peanut oil extracted from new varieties cultivated in Upper Egypt compared to control NC (USA) to find out which varieties are of good quality and are suitable for the Egyptian environment.
2 Materials and methods

Materials
Five genotypes (Tab. 1) of peanuts were grown in Toshka Station, Desert Research Centre, Aswan, Egypt during the summer season of 2017. Peanut varieties namely, Line 27r (Israel), Line 9 (Malawi), Line 4 (Brazil), Line 18 (Israel) and NC (USA) are shown in Table 1. All seeds were brought from the Department of Crop and Soil Science at NC State University, North Carolina, USA and were recommended for cultivation in the arid zone, and irrigated regions of Egypt. The seeds and pod shells were separated manually. The mature and healthy seeds were ground and stored at 4 ± 0.05°C in glass containers for the first day until analysis. All solvents and chemicals were in HPLC grade and purchased from Merck, Darmstadt (Germany). Authentic standards of FAMEs were obtained from Sigma-Aldrich GmbH, Steinheim, Germany.

Chemical analysis
Four peanut genotypes and a control group were analyzed for moisture, protein (% N Â 6.25), ash, fat, and fiber, according to methods described in AOAC (1995). Total carbohydrates were calculated by difference (1) based on dry weight: Total carbohydratesð%Þ¼½100ÀðproteinþfatþashÞ: ð1Þ

Oil Content and Physicochemical properties of peanut oil
Soxhlet apparatus using n-hexane as the solvent was used for the extraction of the oil. The specific gravity of the oil was determined by using pycnometer, and its specific gravity was calculated by the following formula (2): Specific gravity¼density of oil=density of water: ð2Þ The acid, peroxide, saponification, iodine values, and unsaponifiable matter were determined according to standard methods (AOAC, 1995).

Fatty acid composition
The fatty acid composition was determined by the conversion of oil to fatty acid methyl esters prepared by adding 1.0 mL of n-hexane to 15 mg of oil followed by 1.0 mL of sodium methoxide (0.4 mol), according to the method of Nzikou et al. (2009) with some modifications. The mixtures were vortexed for 30 seconds and were allowed to settle for 15 minutes. The upper phase containing the FAMEs was recovered and analyzed by gas chromatography (GC-FID). FAMEs were analyzed on a Perkin Elmer (model 8700), fitted with a non-bonded biscyanopropyle siloxane stationary phase, polar capillary column SP-2340 (60 m Â 0.25 mm), 0.2 mm film thickness and a flame ionization detector. Nitrogen (oxygen-free) was used as a carrier gas at a flow rate of 3.5 mL min À1 . Other conditions were as follows: initial oven temperature, 130°C; ramp rate, 4°C/min; final temperature, 220°C; injector temperature, 260°C; detector temperature, 270°C; temperature hold, 2 minutes before the run and 17 minutes after the run. A sample volume of 1.0 mL was injected. FAMEs were identified by comparing their relative and absolute retention times to those authentic standards of FAMEs. All of the quantifications were done by a built-in datahandling program provided by the manufacturer of the gas chromatograph (Perkin Elmer). The fatty acid composition was reported as a relative percentage of the total peak area.

Statistical analysis
The extracted peanut oil sample analyses were conducted in triplicate. The results presented are the mean and standard deviation of the obtained values. The values of the means were statistically analyzed by SPSS computer software (version 17.0). The calculation occurred by analysis of variance oneway ANOVA and followed by TUKEY honestly test, according to Steel et al. (1997).

Approximate analysis of peanuts varieties
The proximate analysis of the new peanut genotypes and control varieties are shown in Table 2. The obtained results displayed no difference among all the new peanut genotype varieties in moisture content as compared with control: the moisture content ranged from 3.93 to 4.85%. It was noticed that Line 4 and Line 27 have the same value of oil content (50.45 and 50.52%, respectively), which was less than the NC (51.16%); however, line 9 has the highest value of oil content (52.12%). The Line 9 variety was characterized by its higher protein content (28.20%) than that of the NC (control), and Line 18 variety recorded the same value of 26.33%, followed by the Line 27r variety (26.17%) and, finally, the Line 4 variety (25.07%), respectively. The varieties Line 27r, Line 9, and Line 4 showed no significant (p 0.05) difference content in ash (2.78, 2.07, and 2.11%, respectively) as compared with the control (2.80%). The fiber content of the control sample increased significantly to the highest level (71.33%) and decreased to the lowest level (62.33%) in the Line 27r variety. Finally, the carbohydrate content calculated using the difference, and the results clarified that Line 9 variety recorded the lowest level (

Physicochemical properties of different peanut oil varieties
The results obtained from the study are presented in Tables 3 and 4. Table 3 shows the values of the oil properties measured from the extracted oil from the different peanut varieties. The fatty acid contents of the extracted oil were presented in (Tab. 4).

Oil yields
The content of crude oil in the peanut varieties ranged from 50.45 to 52.12% of DW. A little significant variation in the peanut oil content was observed among the five varieties. Line 9 variety contained the highest content of oil followed by NC (control), Line 18, and Line 27r. Line 4 had the lowest oil contents. In the different studies by Hassan et al. (2005), Isleib et al. (2008) and Gulluoglu et al. (2016), it was mentioned that the content of peanut kernel oil ranged from 35 to 56%, according to the genotype and growth factors. Oil percent of peanut species was affected by genotype, seed maturity, growth conditions, geographical area, growing season, and climate status.

Specific gravity
The specific gravity of peanut oil samples ranged from 0.881 to 0.901 (Tab. 3). The obtained data showed that there was no significant difference in all peanut samples. The specific gravity of peanut oil was less than water, and the variance between the oil samples was very small (Shad et al., 2012).

Refractive index
The recorded refractive indices (RI) of peanut oil extracted from different varieties did not significantly vary. The values of RI obtained from the peanut oil samples are similar to those of a wide range of vegetable oils (Arya et al., 1969). The higher measurements of the characteristics reported for the crude oils revealed the necessity to purify the oils. In addition, the high values of oil RI also showed that the oil samples contain long chain fatty acids with a large number of carbon atoms (Bello and Olawore, 2012;Agomuo et al., 2017).

Acidity (free fatty acid percent)
Free fatty acid percent (FFA%) can catalyze oxidative decay of oils by enzymatic and or chemical hydrolysis to form off volatile components. FFA% is an indication of lipase efficacy (Gulluoglu et al., 2016). The FFA% has been calculated according to the molecular weight of the predominant acid. Free fatty acid pointed to the possible hydrolytic retrogression of the oil, and the FFA% was employed to verify the quality and edibility of the oils. According to data illustrated by Aniołowska et al. (2016), the Polish Directive from the Minister of Health from 25 September 2012, the acceptable level of free fatty acids in a frying medium cannot be higher than 2.5 mg KOH g À1 of fat. The free fatty acid percent of the peanut oil samples was within acceptable levels of vegetable edible oils and ranged from 0.33 to 0.42% (Tab. 3). The data revealed that there was little significant variation between the peanut samples.

Peroxide value (PV)
Peroxide value is an indicator of peroxidation, and, therefore, the high peroxide value of the oil is a hint to a weak oil resistance to peroxidation during storage and a signal to a deterioration level (Mohammed and Hamza, 2008;Adebayo et al., 2012). The peroxide number of different varieties of peanut oil has significantly the highest value of 13.05 mEq. O 2 kg À1 for Line 27r variety, while the lowest value of 5.58 mEq.O 2 kg À1 was found for Line 18 variety (Tab. 3). The  peroxide value of all varieties was in acceptable values reported by the Codex Alimentarius Commission (1999). The acceptable levels are up to 10 mEq.O 2 kg À1 of oil for refined oils and up to 15 mEq.O 2 kg À1 of oil for cold pressed and virgin oils. However, the Line 27r variety was higher than the acceptable level. This may be due to the high proportion of unsaturated fatty acids (85.76%) of this variety compared to other varieties. From the results, it was noticeable that Line 4 and Line 18 have lower PV than the control NC.

Iodine value (IV)
The data in Table 3 showed that the iodine value of peanut varieties ranged from 86.71 to 90.90 g 100 g À1 oil in all varieties. The highest iodine value was found in NC (control) variety and the lowest in Line 27r. The iodine number was used to define the degree of unsaturation and stability of peanut oil samples. High-oleic peanut has a longer shelf life than lowoleic peanuts and has the same good flavor and stability of lowoleic peanuts. Escobedo et al. (2015) mentioned that the O/L ratio and iodine value in peanut varieties grown in Mexico varied between 1.8 to 2.1% and 88.6 to 105.4 g 100 g À1 , respectively.

Saponification value (SV)
Saponification values of peanut oil (Tab. 3) were found the highest (194.75 mg g À1 ) for the Line 27r variety and lowest (189.41 mg g À1 ) for NC (control) variety. The saponification number was in the acceptable range of most vegetable edible oils. The saponification number of 200 mg g À1 indicates a high percentage of fatty acids of low molecular weight and carbon chain length. This indicates that the oil may not have a potential for use in soap making and in cosmetics production. This property makes them useful as sources of essential fatty acids required in the human body (Akanni et al., 2005;Elabd et al., 2017).

Unsaponifiable matter (USM)
The bioactive compounds from USM such as polyphenols, phytosterols, tocopherols, and vitamins (soluble in fat) have a potential effect as antioxidants and antimicrobials (Mohamed et al., 2018). Estiasih et al. (2014) reported that USM of palm fatty acid distillate decreased total cholesterol, LDL cholesterol, and triglyceride and increased HDL cholesterol level in hypercholesterolemic rats. The unsaponifiable matter content of peanut oil samples ranged from 0.98 to 1.52%. The highest value of unsaponifiable matter was found in NC (control) variety (1.52%) followed by Line 27r, Line 9, Line 4, and Line 18 (1.26, 1.13, 1.07, and 0.98%, respectively). The unsaponifiable matter percent significantly varied in all the varieties.

Saturated fatty acid (SFA)
The variances among the peanut varieties were statistically significant (at level p 0.05) for saturated fatty acids, such as palmitic (C16:0), arachidic (C20:0), and behenic (C22:0) acids in all varieties. The ranges of fatty acids differ from 12.01 to 15.00% of palmitic acid (C16:0), 0.80 to 0.97% of arachidic acid (C20:0), and 0.94 to 1.30% of behenic acid (C22:0) in all varieties (Tab. 4). Statistically significant variances among peanut varieties were observed for saturated fatty acids in all peanut varieties under study. The saturated fatty acid percent in peanut oil was strongly affected for determined by the genotype (Isleib et al., 2008;Castro and Leite, 2018). The similar results were supported by the data reported by Hassan and Ahmed (2012), Önemli (2012), Mzimbiri et al. (2014) and Escobedo et al. (2015). Hassan et al. (2005) mentioned that the significant difference for saturated fatty acids between peanut cultivars was a characteristic due to the diversity of the genotypes.

Unsaturated fatty acids (UFA)
PUFA to SFA mean ratio recommended by the British Department of Health is more than 0.45, and WHO/FAO experts have reported guidelines for a balanced diet in which the proposed ratio of PUFA/SFA is above 0.4 (Wood et al., 2008). Statistically significant variances at level p 0.05 were found between peanut species for the major unsaturated fatty acids, such as oleic (C18:1) and linoleic acid (C18:2) percentages in all varieties. According to different species, the oleic (C18:1) and linoleic acids (C18:2) percentage ranged from 55.47 to 62.93% and from 19.56 to 24.01%, respectively (Tab. 4). In this investigation, a variation among the peanut species was for oleic acid (C18:1) and linoleic acid (C18:2) percent. Andersen and Gorbet (2002) illustrated that oleic acid (C18:1) percent in peanut genotypes ranged from 21 to 85% and from 2 to 43% in linoleic acid (C18:2). Escobedo et al. (2015) reported that peanut oil is rich in oleic (C18:1) and linoleic acids (C18:2). The composition of peanut oil is affected by several sets of factors that consist of genetic factors, environmental conditions, and interactions between environmental and genetic factors (Andersen and Gorbet, 2002;Isleib et al., 2008;Chaiyadee et al., 2013).

Conclusion
From the obtained data, it could be concluded that the different peanut cultivars maybe are suitable for Egypt's environmental conditions, after conducting some agricultural studies. Among the five varieties, Line 9 had the highest amount of oil content (52.12%) in comparison with the other varieties. Between the five studied cultivars, the oil extracted from Line 27r showed comparatively high O/L ratio (3.22%) and a low iodine value. Among the present peanut cultivars, it could be concluded that Line 27r be the preferable choice for researchers, food scientists, and biochemists, as well as, manufacturers interested in food and nutrition. In addition, the obtained data may be useful for nutritionists and nut consumers when it comes to choosing the best foods and food products.